The Guardian has obtained Facebook’s editors training document that details how FB staff should curate the “trending” headlines tool.

The guidelines show that editors must select trending news from headlines surface via FB’s algorithm, and make sure that they appear on five of ten “trusted” news sources…a news list that includes the New York Times, BBC, CNN and Fox News. On the surface there appears to be no issue with this process, but conservatives will be quick to note that of the ten “trusted” sources, Fox News is the only conservative outlet on the list.

Recode goes more in depth on Facebook’s headline tinkering now commonly known as TrendingGate…

The Guardian notes that the former Facebook editors it spoke to disagreed with the allegations of anti-conservative leanings at Facebook, and that Facebook has since updated its guidelines.

Shortly after this story was published, Facebook VP of global operations Justin Osofsky posted a broad overview of how the Trending Topics tool works, in addition to Facebook’s updated Trending Topics guidelines.

Keeping track of these lists is getting confusing, so here’s a straightforward breakdown of how Facebook uses them to source and write its Trending Topics headlines:
– The RSS feed is a way of identifying stuff that’s trending that isn’t just on Facebook.

– The 1K list has websites that can be used to verify headlines.

– Editors use the 10 outlets list (New York Times, Fox News, CNN, etc.) to figure out how important the story is.

A representative for Facebook directed Recode to a specific line in the leaked guideline, in the “Injecting Topics” section: “The editorial team CANNOT inject a newsworthy topic if it is not appearing in the [news topic] demo or re-view tools.”